The present invention relates to an electric evaporator for insecticides or perfumes, the intensity of which can be adjusted, and in particular to a evaporator for liquid formulations in which the flow of active substance emitted may be continuously regulated between a minimum and a maximum level.
In the field of electric home evaporators used with liquid formulations, evaporators are already known wherein the intensity of evaporation of the active substance may be adjusted by modifying the relative position of the heating devicexe2x80x94which is normally an electric resistance or a PTCxe2x80x94- with respect to that of the wick dipping in the bottle containing the liquid solution of active substance.
These known devices may be divided into different categories which will be briefly examined below, with reference also to the main drawbacks associated therewith.
In a first category of evaporators, the heating device can be moved towards or away from the wick in the bottle containing the active liquid solution, by means of a mechanical device, for example of the screw/nut thread type, so that the heat flow striking the wick itself may be increased or decreased. A device of this type is for disclosed in E-U-8800978. The drawbacks of this type of device are associated with the high manufacturing costxe2x80x94owing to the large number of component parts and the consequent expensive nature of the assembly operations which must be performed, at least partially, by handxe2x80x94and also the safety and duration of the electrical connections between the plug and the heating device, which connections are subject to continuous movement during the evaporator adjustment operations. Moreover, the adjustment of the evaporation intensity is fairly approximate, both as regards the constancy of minimum and maximum levels and above all as regards the repeatability and the linear variation of the intermediate levels. In fact, the movements of the heating device often result in an irregular alteration in the distribution of the heat flow, due to the presence of the various parts of the evaporator which create obstacles to said flow.
In a second category of evaporators, the heating device is fixed and the bottle is displaced along its axis, by a mechanical device, for example of the screw/nut thread type or simply a friction device, so as to increase or reduce the overlapping zone between wick and heating device. A device of this type is for example disclosed in EP-A-0942648 and in it the problems of safety and duration of the electrical connections are overcome. In the case of devices which use a screw/nut thread mechanism there remains the drawbackxe2x80x94already seen for the devices in the first categoryxe2x80x94of the high manufacturing cost, while in the case of devices of the friction type, which have a simpler and more inexpensive design, the main drawback consists in the lack of maneuverability and the instability of the desired adjustment position.
In a third and last category of evaporators, the heating device is fixed to the plug and rotates with it, as disclosed in EP-A-0943344. The body of the plug comprises a screw/nut thread or cam system, so that it allows the axial or lateral displacement of the body itself and consequently of the heating device with respect to the wick, in the various possible positions assumed by the plug. In these devices also the problem of the electrical connections is satisfactorily dealt with, in that the connections are obviously not subject to any movement during rotation of the plug. It remains however the problem of a manufacturing cost which is still too highxe2x80x94although it is lower then that of the devices in the preceding categoriesxe2x80x94due to the fact that a specially designed plug, and not a standard rotatable plug, is used. Moreover, the evaporation adjustment system allows only two-position adjustment, i.e. either a minimum flow or a maximum flow, and therefore it is not possible to adjust with continuity and precision the evaporation flow between a minimum level and a maximum level.
The object of the present invention is therefore to provide an electric evaporator for insecticides or perfumes, of the type for use with liquid formulations, in which it is possible to obtain an optimum and continuous adjustment in the flow of evaporated active substance between a minimum level and a maximum level, without the need for use of complex mechanisms of the screw/nut thread type and also avoiding any displacement of the electrical connections of the heating device during the evaporation-flow adjustment operations.
Another object of the present invention is to provide a evaporator for insecticides or perfumes, in which the bottle containing the liquid active substance may be fixed inside the heating unit in an easy, quick and safe manner; in particular said bottle must offer a high level of safety with regard to accidental removal of the bottle by young children.
These objects are achieved, according to the present invention, by means of an electric evaporator for insecticides or perfumes in liquid formulation, contained in a bottle provided with a wick, of the type in which said bottle can be steadily inserted into a container, the inside of said container being further provided with an element for housing and centering said wick and with a respective electric heating device, characterized in that said wick housing and centering element is fixed to the walls of the container through elastic means which allow displacements of said element in a direction perpendicular to the axis of the wick towards or away from said heating device and in that a cam device which can be actuated manually outside of said container is further provided for effecting said displacements of the wick housing and centering element.